Stokes law - Settling velocity and rate

1. The problem statement, all variables and given/known data
1. A fly ash (ρ =1.8 g/mL) aerosol consists of particles averaging 13 μm in diameter and with a concentration of 800μg/m3. Use the average diameter to calculate the settling velocity (cm/s) and settling rate (μg/m/s) of the particles in air.
The Stokes-Cunningham slip correction factor is 1.015.